The present invention generally relates to semiconductor fabrication equipment and, more particularly, to an apparatus and system integrating the wafer stocking and sorting function for use in a semiconductor processing line.
A conventional semiconductor fabrication plant typically includes multiple fabrication areas or bays interconnected by a path, such as a conveyor belt. Each bay generally includes the requisite fabrication tools (interconnected by a subpath) to process semiconductor wafers for a particular purpose, such as photolithography, chemical-mechanical polishing, or chemical vapor deposition. Material stockers or stocking tools generally are located about the plant and store semiconductor wafers waiting to be processed. The wafers are typically stored in containers, such as cassettes, each of which can hold up to 25 wafers. The cassettes are then stored in carriers that facilitate movement throughout the plant. The carriers can move material in lots, primarily between stocking locations, such as production wafers, test wafers, or empty cassettes if necessary to ensure that the process is moving smoothly.
A material stocker typically services two or more bays and can hold hundreds of cassettes. While not shown, the semiconductor fabrication plant, including the bays, material stockers and the interconnecting path, typically operates under control of a distributed computer system running a factory management program. Another program can be implemented to track and control the movement of material in the carriers throughout the plant.
A typical semiconductor fabrication plant handles the processing of thousands of wafers at any given time. The wafers are typically divided into lots that undergo different processing sequences. Most of the time the mix of material, in the form of lots, moving through the plant includes test wafers and empty cassettes that are moved frequently into and out of the manufacturing line. A more detailed discussion of the movement of lots throughout a semiconductor manufacturing facility may be found in U.S. Pat. No. 5,751,581 issued May 12, 1998 to Tau et al., entitled xe2x80x9cMaterial Movement Server,xe2x80x9d which is herein incorporated by reference.
Cycle time is increased when the wafers have to be sorted prior to being introduced in the line and a wafer sorter is not readily available. Profitable short-term opportunities could be pursued if the manufacturing line were more readily responsive to event changes or management directives. In view of the above, there is a need to integrate such event changes or a management level directives into the production schedule without substantially disrupting the flow of material through the plant, lowering the manufacturing yield or increasing cycle time.
The present invention is directed to addressing the above and other needs in connection with improving efficiencies of wafer stocking and sorting systems.
The present invention is exemplified in a number of implementations and applications, some of which are summarized below. It has been discovered herewith that reduced cycle time can be realized by having the capability of sorting a wafer lot while at a stocking location irrespective of other operations on the processing line, as described in various aspects below. Further, based on the type of wafer lot being processed, the stocker/sorter apparatus can automatically make wafer adjustments with respect to certain recipes or conduct a recovery operation (in case of a loss of power) without having to seek out a separate wafer sorter. Accordingly, a wafer stocking and sorting apparatus that addresses this need of reducing cycle time and reduces the need for excessive handling of delicate wafers that can lead to a reduction in manufacturing yield is described herein.
In one aspect of the invention, the apparatus includes a scanning arrangement that scans wafers and wafer carriers to identify codes located on the wafer carriers that indicate the position of a wafer within the carrier and by slot. A sorting arrangement sorts wafers and carriers within storage bins located in an enclosure. The apparatus also includes a computer arrangement that controls the scanning and sorting arrangements and stores data retrieved therefrom, the data being used for wafer selection and for tracking wafer movement from the start of processing.
According to another aspect of the invention, a system for storing and sorting wafers in a wafer processing system includes a plurality of stocking locations for wafers and cassettes; a plurality of carriers having wafers and cassettes disposed therein; an apparatus for stocking and sorting wafers adapted to track wafer movement from the start of processing and to select wafers as a function of an externally provided directive; and a conveyor arrangement for moving wafers from one of the stocking locations to a processing location.
In yet another aspect of the invention, an apparatus for storing and sorting wafers for use in a wafer processing system includes a scanning device for scanning wafers and wafer carriers. The scanning device identifies codes located on the wafer carriers that indicate the position of a wafer within the carrier and by slot. A robotic arm sorts wafers and carriers within storage bins located in an enclosure. A computer arrangement controls the scanner and the robotic arm and stores data retrieved therefrom, the data being used for wafer selection and for tracking wafer movement from the start of processing.
In yet another aspect of the invention, a method for storing and sorting wafers for use in a wafer processing system includes scanning wafers and wafer carriers by identifying codes located on the wafer carriers that indicate the position of a wafer within the carrier and by slot. The wafers and carriers are sorted within storage bins located in an enclosure and a computer arrangement controlling the scanning and sorting and storing data retrieved therefrom is then used. The data retrieved is used for wafer selection and for tracking wafer movement from the start of processing.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures in the detailed description that follow more particularly exemplify these embodiments